可以用Collections.addAll(list,a)或者list = Arrays.asList(a)方法将一个数组转换成List

public class Test {
    public static void main(String[] args) {
//        int[] a = {1,2,3};  //基本类型的数组不行，会报错
        Integer[] a = new Integer[]{1,2,3};
        List<Integer> list = new ArrayList<>();

//        Collections.addAll(list,a);
        list = Arrays.asList(a);

        System.out.println(list);
    }
}

输出

[1, 2, 3]